High Efficiency X-ray Fluorescence Detectors

描述(申请人提供)：目前已达成普遍共识，即迫切需要开发更好的XAS探测器系统，以解决探测器落后于同步加速器源的问题。采用线性梯度多层膜的多层分析器阵列探测器(MAAD)已经成功地用于处理来自第三代光源的大光子通量。然而，该类型探测器的探测立体角有限，受其垂直和水平接受能力的限制。如果水平接受角从目前的0.4弧度水平增加，探测器将遭受巨大的吞吐量损失以及能量分辨率的降低。一方面是计数率限制，另一方面是探测立体角的探测情况，不仅限制了强大的第三代和超同步辐射光源的有效利用，而且给生物样品带来了过量的辐射负担。我们现在建议通过在多层阵列探测器设计中使用“径向梯度多层膜”(而不是线性梯度多层膜)来显著增加水平接受角。这将使立体角比线性渐变MAAD增加2.5倍，而不会使探测器设计太复杂。此外，径向梯度多层探测器的吞吐量将有实质性的提高，能量分辨率将大大降低。将荧光探测器的优值定义为立体角和吞吐量除以能量分辨率的乘积，新设计的优值比原来提高了5~10倍。该探测器具有较高的能量分辨率和较大的立体角，在软X射线区是非常理想的探测器。在第一阶段，我们将制作一个由两个径向梯度多层膜组成的探测器原型，并将评估其在2-8keV能量范围内的性能。第二阶段项目将开发阵列探测器，使其覆盖总立体角的5%-10%，并在大能区运行。将窄带多层膜技术与双多层分析技术相结合，可使系统具有很高的背景抑制能力。

DESCRIPTION (provided by applicant): It has become a general consensus that the development of better XAS detector systems is urgently needed to solve the problem of detectors are lagging behind synchrotron sources. The multilayer analyzer array detector (MAAD) using linearly graded multilayers has been successfully developed to handle the large photon flux from the third generation sources. However, this type of detector has limited detection solid angle restricted by its vertical and horizontal acceptance. The detectors will suffer large loss of throughput as well as degraded energy resolution if horizontal acceptance angle is increased from the current 0.4 radian level. The detection situation, with count rate limitation at 1 hand and the detection solid angle at the other, not only limits the effective use of the powerful third generation and beyond synchrotron sources, but also puts excess radiation burden on biological samples. We now propose to substantially increase the horizontal acceptance angle by using "radial gradient multilayers" (instead of linearly gradient multilayers) in the multilayer array detector design. This will give a 2.5 times of solid angle increase over the linearly graded MAAD without too much complication in the detector design. Furthermore, the radial gradient multilayer detector will have a substantial improvement in throughput, and a large reduction in energy resolution. Defining the Figure of Merit of the fluorescence detector as the product of solid angle and throughput divided by the energy resolution, the Improvement of the Figure of Merit of the new design is 5 to 10 times. The detector is very desirable in the soft x-ray region due to its superb energy resolution and large solid angle. In Phase I, we will fabricate a prototype detector consists of 2 radial gradient multilayers, and will evaluate its performance in 2-8 KeV energy range. The Phase II project will develop the array detectors to cover a 5-10% of total solid angle and to operate in a large energy region. Combining narrow bandwidth multilayers with dual multilayer analyzer technique, the system can be made with very high background rejection capability.